I was never able to do things the easy way, so I decided to upgrade a few things on this kit.  I started building in late March of 2023, beginning with the fins by applying sanding sealer.  Each fin warped like a potato chip.  I had also acquired my first 3d printer shortly before and set out to print the fins as a way to learn some of the supporting software.  I had to take a break to build some other models with my son.

I returned back to the model in late April and decided to add centering rings, a motor retaining ring, and a shock cord hook, all 3D printed.

I followed the instructions for the kit but tack-glued the fins to the body tube with medium CA glue.  I followed this with epoxy fillets and included micro ballons to thicken the 15-minute epoxy.

I attached the shock cord mount halfway in the body tube coupler with epoxy after attaching the 80 inches of shock cord.

Once the shock cord epoxy was cured, I connected the fin can to the payload body tube with the coupler using wood glue.

Finally, I applied a film of thin CA glue to the forward end of the payload body tube to strengthen it.

All 3D parts were printed with PLA+ on a Creality Ender 3 v2 Neo.

I will post all the STLs on Printables and provide a link here, once it's completed (unless it goes up in a blaze of glory).

Had two launches today (5/7/2023). 

The maiden flight was on D12-5.  The estimated altitude was ~35m.  It was very slow coming off the launch pad.  I suspect the thrust to weight was pretty low but it was stable.  The parachute failed, which has now become a tradition on maiden flights, so it potatoed but appeared in good condition

2nd flight was on an E20-7 and the altitude was 300m.  I discovered that one fin was lifting off and may have been damaged suffered during the maiden flight.

Post-Flight Analysis:

Regarding the 3D-printed parts:  Everything worked very well.  MMT is obviously sealed, so the inspection is on only the Aft centering ring and motor retainer, but both suffered no damage due to heat.  The shock cord hook appears to be in good condition as well.  I will definitely be printing more parts for hard-to-find / custom parts, or to add strength. 

Overall, this was a fun model.  I am really happy I upped the MMT from 18mm to 24mm b/c the D12 was barely enough to get it into the sky.  However, I should have considered through-wall fins.  It may not have prevented the damage but it limits the amount of thrust I can push through this rocket, which is a solid flyer.  The sweet spot seems to be 20-40N of thrust.  I am gonna try ramping up the thrust to see where the breaking point is.  If I can get an F36 (~60N thrust) to launch successfully, then I will call this a complete success.  Also, I am using kevlar thread for the shock cord, but I think it is too thin and will eventually fail.  I would like to upgrade this to 3mm and if the cord does fail, I will do so at that time.

I will repair the fin and reinforce the others with another fillet of epoxy and get it back in the air ASAP. #FTW